Dolly for drill sharpeners



Patented July 14, 1931 UETED TATES CHARLES LARSON, F BAXTER SPRINGS, KANSAS, ASSIGNOR TO INGERSOLL-RAND OOM- PAT T OFFICE PAN'Y, OF JERSEY CITY, NEW JERSEY, A CORPORATION OF NEW JERSEY DOLLY FOB DRILL SHARPENERS Application filed. July 27, 1 928. 7 Serial No. 295,720.

This invention relates to sharpening mechanism, but more particularly to a dolly used in mechanism of this type for forming the cutting edges on drill bits and similar articles.

One object of the invention is to prevent breakage of the forming teeth of the dolly. This is accomplished by so forming the teeth as to prevent contact between the teeth and the clamping dies whereby the implement intended to be sharpened is held.

Other objects will be in part obvious and in part pointed out hereinafter.

In the drawings illustrating the invention and in which similar reference characters refer to similar parts, 1

Figure 1 is a sectional elevation of a portion of a drill sharpener having the invention applied thereto,

Figure 2 is a transverse view taken through Figure l'on the line 22 looking in the direction indicated by the arrows, and

Figure 3 is a longitudinal sectional View taken through Figure 2 on the line 33 looking in the direction indicated by the arrows.

Referring more particularly to the drawings, A and B represent top and bottom clamping dies seated in coacting die holders C and D respectively. The die holders C and D may be of a well known type commonly used in drill sharpeners, the bottom die holder D being stationary and the die holder C reciprocable relatively to the die holder D in order to lower and raise the clamping die A for the purpose of clamping a working implement E between the dies or to release said working implement.

The working implement illustrated is intended to represent a drill steel which lies in oppositely disposed recesses F in the dies A and B The formation of the recesses F preferably corresponds to the contour of the implement intended to be sharpened. In the T case where a drill steel, such as that illustrated, is the implement intended to be operated upon the rearward portion G of the recesses F are of straight semi-cylindrical form to accommodate the body portion H of the drill steel. The forward portions J of the recesses Fare of conical form to accommodate the bit end K of the drill steel. Preferably both the portions G and J of the recesses are so formed as to insure contact at all points with the outer surface of the drill The drill bit K therefore has four wings Q and between adjacent wings are longitudinal grooves R formed in a previous forging operation In order to form the cutting edges 0 and P it is customary to employ percussive means, such as a cylinder S having a hammer piston T which reciprocates in the cylinder S for actuating a dolly U disposed slidably in thefront end of the cylinder S. The percussive element, only a portion of which is shown, may be suitably mounted on the sharpening mechanism of which the die holders D and C form apart or, if desired, may be independently mounted in such position that the percussive element will be in coaxial alignment with the clamping dies A and B.

The dolly U comprises a stem V which extends into the cylinder S and into the path of the piston T, and ahead W on the front end of which are forming teeth X having inclined sides Y to form similar inclined su'r'faces'Z on the front ends of the wings Q.

Usually in dollies of the type illustrated the head U is provided with a cylindrical surface 6 adjacent the stem V and the portion forwardly of thecylindrical surface I) is of conical form corresponding to the conical'portion's J of the recesses F. The sides or ends 0 of the forming teeth X accordingly form a continuation of said conical surface of the head and when the dolly is driven into the conical recesses J the entire conical surface of the dolly may be brought in body contact with the conical recesses J.

l/Vith the dolly thus constructed it happens not infrequently that the forming teeth X will be driven sharply against one or the other of the dies A and B, thus resulting in breakage of the forming teeth. In order to avoid injury to the dolly the conical surface 0 of the dolly head U is inclined with respect to a contiguous conical surface (1 lying rearwardly of the forming teeth X and the forming teeth X preferably lie wholly within the conical surface 0.

The difference of angularity between the conical surfaces 0 and d may be of any suitable degree, but is preferably such that when the dolly is driven into the dies A and B only the conical surface d may contact with the conical portions J of the recesses F. In this Way there will eXist a slight clearance be tween the conical surface 0 and those of the conical recesses J. Such clearance while sufrlcient to prevent contact between these elements may however, be only slight, thus avoiding the formation of fins or undesirable enlargements at the outer ends of the cutting edges of the drill bit. In practice it has been found that by inclining the conical surface 0 three or four degrees from the conical surface 03 the objects sought may be readily attained Without deforming any portion of the cutting bit of the implement intended to be sharpened.

Due to the present invention breakage of the forming teeth X has been entirely eliminated since whenever one or both of the dies A and B are slightly mis-aligned so that it may not readily be detected by the operator only the solid portion of the dolly rearwardly of the forming teeth X will contact with the clamping dies.

I claim: 7

1. A dolly comprising a head having a frusto-conical portion, there being a forming element on one end thereof, and a conical peripheral surface on said element and of greater degree of inclination than the frustoconical portion.

2. A dolly comprising a plurality of integral portions having contiguous peripheral surfaces of different degrees of inclination, there being a forming element wholly Within the portion of greater inclination.

3. A dolly comprising a head having a plurality of adjoining frusto-conical surfaces inclining in the same general direction there being a forming element on the small end of the head.

In testimony whereof I have signed this specification.

CHARLES LARSON. 

